The Application Of The Ferroin Color-change Method To Evaluation Passivation Quality Of Stainless Steel Facilities In Nuclear Power Plant

Austenitic stainless steel is an important structure and functional material for nuclear power plant. It is characterized by good corrosion resistance, low radiation sensitivity and comprehensive mechanical properties. The quality of passive film on the surface of stainless steel determines the corrosion resistance of the parts in the harsh environment such as the ocean atmosphere environment and sea water, which is one of the key factors influencing the reliability of the equipment. However, in the nuclear power plant equipment manufacturing and engineering stage because the iron contamination, the passivation film is not complete, its corrosion resistance decreased, resulting in valve, fuel rack, stainless steel pipe and other parts pitting, crevice corrosion and corrosion events occurred, corrosion influence nuclear power engineering construction schedule and stainless steel related equipment, safe and stable operation of the system.Quality inspection of nuclear power equipment surface passivation is nuclear power equipment manufacturers and nuclear power plant project, the operational phase of anti pollution, cleaning and passivation of effective means of evaluating, an important part of nuclear power station is the equipment of various stages of quality control. Standard and related industry standards for austenitic stainless steel surface iron contamination and existing stainless steel passivation film quality inspection principles and characteristics of the provisions of. From laboratory tests and on-site application angles compared the blue point method and Ferroin colorimetry, in nuclear power plant site through Ferroin and blue solution in stainless steel valves, piping, welding equipment surface contamination and passivation film detection compares the uses and for the nuclear power station engineering and operation stage of the passive film on stainless steel quality testing provides an effective means. Its conclusions are as follows:(1) laboratory detection reagent electrochemical properties and surface morphology analysis showed that adjacent Ferroin solution on the surface of stainless steel, has higher corrosion potential and lower corrosion rate than the blue solution; blue reagent for no passivation of stainless steel with localized corrosion potential injury risk.(2) the detection sensitivity of the laboratory and nuclear power plant site tests showed that the detection sensitivity of the detection of the adjacent Ferroin is high, safe and stable; but the blue point reagent is not stable, which can produce the detection error and the two pollution.(3) the ortho ferroin significantly color method of stainless steel valves, piping, welding and other equipment detection results show that explicit comparison and application of color of law for nuclear power plant improve production preparation and operation stage equipment, stainless steel surface contamination detection quality, improve equipment inspection rate and accurate rate, reduce the risk of corrosion of stainless steel equipment; at the same time for stainless steel equipment manufacturing and processing technology provides technical reference.